/Engine/Source/Runtime/GeometryFramework/Public/UDynamicMesh.h
UDynamicMesh::Reset()is called on the object returned to the Pool, which clears the internal FDynamicMesh3 (which uses normal C++ memory management, so no garbage collection involved) So the Pool does not re-use mesh memory, only theUObjectcontainers.
class UDynamicMeshPool : public [UObject](API\Runtime\CoreUObject\UObject\UObject)
TArray<TObject...
AllCreatedMeshes
All meshes the pool has allocated
TArray<TObject...
CachedMeshes
Meshes in the pool that are available